This application claims the Jan. 28, 2002 priority date of German application 10203151.7, the contents of which are herein incorporated by reference.
The present invention relates to an apparatus for connecting semiconductor modules, in particular memory banks.
Printed circuit boards (PCBs), in particular for receiving memory modules, often have features which allow a plurality of population variants for different requirements. One example of such a population variant is a printed circuit board module which is provided with one or two memory banks.
In the case of present-day printed circuit boards or populations of printed circuit boards, the DRAM memory modules of a second bank that is optionally to be mounted are simply not mounted, an unterminated stub remaining which brings about undesirable reflections on the line and represents a small electrical dipole which radiates in an undesirable manner. A further customary embodiment consists in providing in each case a separate printed circuit board for application with one memory bank or two memory banks (DRAM memory module), which results in an increased outlay for the stock keeping and the development of two separate boards. A further possibility consists in linking the optionally required stubs for an optional second memory bank by means of zero-ohm resistors if a second bank (DRAM memory) is inserted on the printed circuit board, the additional zero-ohm resistors leading to complex layout structures on the printed circuit board, particularly if the branch junctions to the optional stubs lie below the DRAM memory modules.
FIG. 1 illustrates a customary arrangement for linking two semiconductor memory banks 1, 2, e.g. on a printed circuit board. By means of a printed circuit board connecting terminal 12 (etch [sic] connector), two bidirectional data lines 10, 11 are connected to soldering contacts 13b,c,e,f, which provides the contact-connection points for a resistor module 3 with two resistors (R2 pack). By means of a continuation of the two bidirectional data lines 10, 11, a memory bank 1 is linked by means of a layer 5 of the printed circuit board, a further memory bank 2 being linked by means of two vias 7 and consequently by means of a second layer 6 and stubs situated thereon. Consequently, the two memory banks 1, 2 or the receiving devices A, B thereof are connected to bidirectional data lines 110, 111 by means of common resistors of the resistor module 3 (R2 pack).
FIG. 2 shows the same arrangement as FIG. 1, but without the mounting of the second memory bank 2. In the absence of a second connected memory bank 2, two unterminated stubs 8 remain, to which the signal of the bidirectional data lines 10, 11 is nevertheless applied. As a result, undesirable reflections and thus signal corruptions can occur at the line ends, which reduces the signal quality of the data read in and out.
It is an object of the present invention to provide an apparatus for connecting semiconductor modules, in particular memory banks, which ensures an improvement in the data quality in conjunction with a low outlay on circuitry.
The idea on which the present invention is based consists in using the same soldering contacts (soldering pads) for a connection module, e.g. with two and four resistors (2- and 4-R pack).
In the present invention, the problem mentioned in the introduction is solved in particular by virtue of the fact that the connection module connects contacts in such a way that only lines which lead to a connected semiconductor module are contact-connected in each case.
Advantageous developments and improvements of the respective subject matter of the invention can be found in the subclaims.
In accordance with one preferred development, a printed circuit board on which the apparatus is situated has at least two different printed circuit board layers by means of which the semiconductor modules, in particular memory banks, or devices for receiving the semiconductor banks or components are contact-connected.
In accordance with a further preferred development, the semiconductor modules comprise semiconductor memory elements, in particular (DRAM) memory banks.
In accordance with a further preferred development, the connection module has resistors.
In accordance with a further preferred development, the connection module has a separate resistor in each case per connected memory bank and data line.
In accordance with a further preferred development, the apparatus with two connected semiconductor modules, in particular memory banks, has a connection module with four resistors.
In accordance with a further preferred development, the apparatus with an individual connected semiconductor module has a connection module with two resistors.
In accordance with a further preferred development, the lines are data lines, in particular bidirectional data lines.
In accordance with a further preferred development, the contacts of the connection module are soldering contacts.
In accordance with a further preferred development, a group of contacts of the connection module are connected to a plug contact/printed circuit board connecting terminal (etch [sic] connector) by means of lines.
Exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the description below.